A 41-year-old woman presented with progressive fluctuating lower limb weakness, urinary incontinence, and dry eyes and mouth. Physical examination revealed proximal flaccid tetraparesis (Medical Research Council 4). The patellar reflex was absent, but with postexercise facilitation (video 1). Eyelid and eye movements were normal. Electroneuromyography revealed a presynaptic neuromuscular junction disorder (figure). Antibodies to anti-voltage-gated calcium channels were positive. Periodic cancer screening, including whole-body FDG-PET, was negative during 2 years of follow-up. These findings were consistent with nonparaneoplastic Lambert-Eaton myasthenic syndrome.1 The patient had a good response to IV immunoglobulin. The presence of ascending muscle weakness, autonomic dysfunction, and postexercise facilitation of reflexes should raise suspicion for the diagnosis.
Video 1
Facilitation of patellar reflex in Lambert-Eaton myasthenic syndrome. The first part of the video shows the patient with absent patellar reflex that was elicited after a sustained muscular contraction, known as postexercise facilitation. In the second part of the video, the patient presents a normoactive patellar reflex after treatment. Absent/reduced reflex, as well as postexercise facilitation of reflex, are specific clinical clues to the diagnosis of Lambert-Eaton myasthenic syndrome.Download Supplementary Video 1 via http://dx.doi.org/10.1212/012180_Video_11
(A) Low-frequency repetitive nerve stimulation shows a decremental response (31.6%) at 3 Hz. (B) High-frequency repetitive nerve stimulation shows an incremental response (164%) at 30 Hz. (C) Compound muscle action potential amplitude increment of 400% after a 10-second exercise (postexercise facilitation).
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↵* These authors contributed equally to this work.
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